The present invention belongs to the field of plasma display panels (hereinafter also referred to as xe2x80x9cPDPxe2x80x9d) and, more particularly, it relates to an apparatus for producing a substrate for PDP, a mold used in such production apparatus, and a method of producing a substrate for PDP.
Recently, thin display devices such as PDPs have been developed intensively. Because PDPs are thin and can also provide a large image plane, high image quality and wide viewing angle can be achieved as compared with a typical thin display device such as liquid crystal display.
Generally, PDP is equipped with a substrate. Typical substrates for PDP is composed of a pair of glass flat plates facing each other at a distance via ribs each having the same dimension (also referred to as a barrier rib, bulkhead or barrier). Such ribs of the substrate for PDP with such a constitution can partition the space between a pair of glass plates in an air-tight manner to form a plurality of discharge display cells capable of containing a gas, which emits light by discharging, such as neon, helium or xenon.
Describing the substrate for PDP in more detail, as shown in FIG. 10, the substrate 10 for PDP has such as constitution that electrodes 2 are disposed in parallel with each other at a fixed distance on a glass plate 1 and each rib 3 is provided thereon. The electrodes 2 may be coated with a dielectric layer so as to avoid sputtering of the electrodes due to discharging of a gas, if necessary. In the embodiment shown in the drawing, each rib 3 is provided between the electrodes 2 in a state of being integrated with a dielectric layer 4.
Various methods of producing ribs of the substrate for PDP have been known. For example, Japanese Unexamined Patent Publication (KOKAI) No. 9-122336 discloses a method using a mold. According to this method, the ribs are produced by coating the whole surface of a mold or a glass plate with a curable pasty precursor of the ribs (hereinafter also referred to as a xe2x80x9crib precursorxe2x80x9d). The mold and glass plate were then closely contacted with the rib precursor disposed between. Next, the rib precursor was cured and molded to obtain desired ribs.
The mold used in this method of producing the ribs is made of glass or metal. Generally, it is necessary to use a mold produced with high working accuracy in case where the mold and glass plate are closely contacted each other, uniformly. Otherwise, there is a tendency that a non-uniform dielectric layer may be molded integrally with the ribs. In case where the glass plate or mold have a comparatively wide area, this undesired tendency is increased. According to this method, there is a fear that, when the mold is removed from the glass plate, peeling of the ribs from the glass plate can occur, thereby making it impossible to properly transfer the ribs to the glass plate. This is because a comparatively large force must be applied to the mold due to the above-described rigidity
On the other hand, Japanese Unexamined Patent Publication (KOKAI) No. 9-12336 discloses that entrapping of air bubbles between the mold and glass plate is prevented by close contact between the mold and glass plate under reduced pressure. It is usually required to use a pressure reducing device accompanying complicated constitution and complicated handling for such pressure reduction The pressure reducing device is large in size and often requires additional equipment. Close contact under reduced pressure requires not only a wide space for such equipment, but also complicated step and skill.
Japanese Unexamined Patent Publication (KOKAI) Nos. 8-273537 and 8-273538 disclose a method of producing ribs by using a mold having pliability Describing in more detail, Japanese Unexamined Patent Publication (KOKAI) No. 8-273537 discloses that a mold is filled with a rib precursor using a blade and then this mold is closely contacted with a glass plate. On the other hand, Japanese Unexamined Patent Publication (KOKAI) No. 8-273538 discloses that the whole surface of a glass plate is previously coated with a rib precursor and then a mold is closely contacted with the glass plate. However, according to both of these methods, there is a tendency that air bubbles are entrapped between the mold and plate upon close contact. Such entrapment of air bubbles is likely to introduce defects into the ribs. Particularly, in case where the substrate for PDP has a wide area, many defects can occur. As disclosed in Japanese Unexamined Patent Publication (KOKAI) No. 9-12336, a suggestion of avoiding entrapment of air bubbles by closely contacting the mold with the glass plate under reduced pressure is made. However, as described above, use of the pressure reducing device requires wide space and skill, which is not preferred.
It is, therefore, an object of the present invention to provide an improved method of and an improved apparatus for producing a substrate for PDP, which can easily reduce nonuniformity of a dielectric layer and defects of ribs.
Another object of the present invention is to provide a mold which can be advantageously used in the method and apparatus.
According to the present invention, there is provided an apparatus for producing a substrate for plasma display panel comprising a plate and ribs provided on the plate, which comprises:
a table for the plate,
a rib precursor supplying portion for providing a precursor of the ribs on the plate,
a pliable mold having at least groove portions provided in parallel with each other at a fixed distance, which is disposed on the precursor of the ribs provided on the plate,
a mold pressing portion for applying a pressure to the mold, thereby to contact the mold closely with the plate via the precursor of the rib, and
a driving portion for moving the mold pressing portion along the groove portions of the mold.
According to the present invention, there is also provided a mold for use in the production of a substrate for plasma display panel, which is subjected to antistatic finish.
According to the present invention, there is also provided a mold for use in the production of a substrate for plasma display panel, comprising:
an acrylic base material,
an ionic conductive substance dispersed in the acrylic base material, and
a medium which is dispersed, thereby making it possible to ionize the ionic conductive substance.
In addition, according to the present invention, there is provided a method of producing a substrate for plasma display panel comprising a plate and ribs provided on the plate,
(A) which comprises the steps of:
a rib precursor supplying step of providing a precursor of the ribs on the plate,
a rib precursor filling step of filling a pliable and antistatically treated mold having at least groove portions provided in parallel with each other at a fixed distance, with the rib precursor,
a rib precursor molding step of curing the rib precursor to form a molded article, and
a rib molded article transferring step of removing the mold and transferring the molded article to the plate, and
(B) in which:
the mold is pressed along the groove portions from one end to the other end of the groove portions provided thereon in the rib precursor filling step.